The present invention relates to a wheel alignment measuring apparatus with six angle measuring instruments whose outputs are joined up with an electronic signal processing unit.
In the prior art, wheel alignment measuring apparatus has been made with freely moving turntables which are placed under the steering wheels of a vehicle and which has a number of different measuring instruments to be fixed to the steering wheels and giving readings for toe-in and camber and furthermore for giving a reading for the tracking difference angle, that is to say the angle of the steering wheel which may be though of as being on the inside on turning a corner, at a steering angle of -20.degree. of such wheel, for the caster (that is to say the slope of the king pin or the axis of turning of the wheel as seen from the side of the vehicle), and the king pin angle, that is to say the slope of the king pin in a plane normal to the length direction of the vehicle to an upright.
On changing the steering angle of the front wheels the slope of the wheel plane, that is to say the camber, is changed while at the same time the slope of the unmoving wheel is changed. On the basis of these changes between two equal angles of steering, that is to say equally far from the straight ahead position, readings are produced for the caster and the king pin angle. For this reason the angles of steering have to be able to be extactly measured.
For producing a reading for these steering angles of the front steering wheels, such wheels are placed on turntables whose top turning parts have scales which cooperate with pointers fixed to the fixed lower parts of the turntables. For each measuring operation the scale has to be moved separately for each side of the vehicle in relation to the pointer, which may have a vernier, till a zero reading is produced. After this working step, the wheel has to be turned into the desired steering angle position, it being necessary for the worker to undertake these steps directly on each wheel on each side separately, the use of the steering wheel not being possible because it is then not possible to see any reading for the steering angle.
Quite separately from the steering motions of the front wheels, it is furthermore necessary to make adjustment and to take readings at different further angle measuring units, and it is only after changing over the steering angle of the front wheels to the other direction that complete and true figures for the wheel alignment angles are produced.
Taking readings for the track difference angle, caster and toe-in has to be done separately, first on the one side and then on the other. It may well be that up to twenty working steps will be necessary for measuring wheel alignment if the worker has to go from one side of the vehicle to the other six to eight times.